Abstract
The L10 FePt thin film with high magnetocrystalline anisotropy constant is considered as a potential candidate for the next-generation of high-density magnetic recording materials. To realize the application of the FePt films as perpendicular magnetic recording media, it is necessary to obtain L10 FePt film with a perpendicular magnetic anisotropy. However, the close-packed plane of fct structure is (111), the FePt film normally has (111) preferred orientation and the easy axis incline towards film plane. In this study, we investigate the effect of epitaxial and nonepitaxial growth mechanism on microstructures and magnetic properties of FePt films with perpendicular magnetic anisotropy. In the first topic, single-layered Fe100-xPtx films with various thicknesses were deposited directly on substrates at different temperatures, and the effects of Pt content, substrate temperature and film thickness on microstructures and perpendicular magnetic properties of FePt films were investigated. It was found that nonepitaxial single-layered Fe54Pt46 film with a thickness of 30 nm by in-situ depositing at 620 °C showed strong (001) preferred orientation and good perpendicular magnetic properties (perpendicular coercivity of 14.0 kOe, saturation magnetization of 473 emu/cm3 and perpendicular squareness of 0.96, respectively). In the second topic, the perpendicular magnetic anisotropy degrades when a 5-nm NiO film is introduced under this single-layered FePt film. Upon further increasing the thickness of the NiO film to 10 nm, the perpendicular coercivity of the FePt film decreases greatly to around 4.2 kOe. Compared to a NiO underlayer, the perpendicular coercivity of the FePt film remains above 12.5 kOe when a 10-nm MgO underlayer is introduced. Furthermore, when the thickness of the MgO underlayer is decreased to 5 nm, the perpendicular magnetic anisotropy of the FePt film is further enhanced. The perpendicular coercivity not only stays high at 13.6 kOe, but perpendicular squareness also increases significantly to 1. In the third topic, single-layered FePt films with various peak power density was deposited directly onto Corning 1737 glass substrate by high power impulse magnetron sputtering. The films were then post-annealed at 550 - 700 °C for 30 min. It is found that the perpendicular magnetic anisotropy of FePt films was enhanced greatly by increasing the peak power density from 1196 to 3538 W/cm2. On the other hand, the 10-nm FePt thin films with fine grain can be obtained as the post-annealing temperature was decreased to 600 °C for 30 min. Its perpendicular coercivity, perpendicular squareness, magnetocrystalline anisotropy constant and average grain size are 6.5 kOe, 0.99, 3.1 × 107 erg/cm3 and 6.1 nm respectively, which reveal its promising potential as perpendicular magnetic recording media for high-density recording.